206 research outputs found
Dynamic Docking Test System (DDTS) active table computer program NASA Advanced Docking System (NADS)
A computer program was developed to describe the three-dimensional motion of the Dynamic Docking Test System active table. The input consists of inertia and geometry data, actuator structural data, forcing function data, hydraulics data, servo electronics data, and integration control data. The output consists of table responses, actuator bending responses, and actuator responses
Re-analysis of the Levanluhta skeletal material : Sex and stature estimation of individuals in an Iron Age water burial in Finland
Levanluhta, an Iron Age water burial site in Finland, and its material consisting of commingled skeletal remains and artifacts, has been studied by several researchers over the past 100 years, resulting in multiple interpretations of the people and the site. Previous skeletal analyses have concluded that the majority of the individuals represented in the remains were females and children and were of relatively short stature, so possibly nutritionally deprived. This study re-analyzed the commingled adult human remains with updated methods. The methods applied in this study to estimate sex and stature were based on more representative European reference samples than the previously applied methods. The methods included morphology, osteometrics, and computed tomography (CT) scans. Our results indicated that depending on the reference data, the majority of the individual adult bones including os coxae (73%, n = 45) and long bones (humerus 83%-89%, n = 52; radius 72%-89%, n = 47; ulna 50%-65%, n = 58; femur 92%-100%, n = 25; tibia 77%-85%, n = 26) were classified as females based on their size and morphology. The cross-sectional bone properties of humerii, femora, and tibiae visualized using CT scanning also supported these findings. However, the cranial morphology did not show as clear female-biased sex ratio as other methods (42% females, 33% males, 24% undetermined, n = 33). In females, the mean stature based on the tibia (155.3 cm, n = 10) was within the range of the coeval European females and did not necessarily indicate nutritional deprivation, which is in line with previously published stable isotope findings from the site. The mean stature based on the tibia suggested that the Levanluhta males were short (164.0 cm, n = 3), but final interpretations were limited due to the small number of male individuals. The current study affirmed that the Levanluhta skeletal assemblage was female biased and gave new insights into interpretation of the stature.Peer reviewe
Influences on achieving motor milestones: A twin-singleton study
In order to determine if twinning impacted achievement of motor milestones the attainment of early motor milestones in twins was examined and compared to published data from singletons of the same age from the same culture and birth years. We examined the influence of twinning, sex, zygosity and birth cohort (1987-2001) on the motor development of twins aged 0 to 24 months. Data on the attainment of motor milestones (turn, sit, crawl, stand and walk) of twins were collected from maternal reports. All data were corrected for gestational age. Data from the twin sample were compared to normative data from singletons, which were available from Child Health Clinics (CHC). Analyses across twin data and the CHC singleton data revealed no differences between twins and singletons in achievement of motor milestones. Girls were able to sit without support slightly earlier than boys, otherwise there were no other sex differences. Birth-order analyses revealed minimal but significant differences in turning over from back to belly and for sitting without support between the first- and second-born. Dizygotic (DZ) twins were faster than monozygotic (MZ) twins in achieving the moment of sit, crawl, stand and walk. Twins born in earlier cohorts were faster in reaching the moment of crawl, sit and walk. It is concluded that there are no differences in time of reaching motor milestones between twins and singletons within the normal range. Sex has minimal to no effect on motor development in early childhood. DZ twins achieve motor milestones sooner than MZ twins. Attainment of gross motor milestones (crawl, stand and walk) is delayed in later birth cohorts
Change in Terrestrial Human Footprint Drives Continued Loss of Intact Ecosystems
Human pressure mapping is important for understanding humanity's role in shaping Earth's patterns and processes. We provide the latest maps of the terrestrial human footprint and provide an assessment of change in human pressure across Earth. Between 2000 and 2013, 1.9 million km2 of land relatively free of human disturbance became highly modified. Our results show that humanity's footprint is eroding Earth's last intact ecosystems and that greater efforts are urgently needed to retain them
Using multiscale lidar to determine variation in canopy structure from African forest elephant trails
Recently classified as a unique species by the IUCN, African forest elephants (Loxodonta cyclotis) are critically endangered due to severe poaching. With limited knowledge about their ecological role due to the dense tropical forests they inhabit in central Africa, it is unclear how the Afrotropics are influenced by elephants. Although their role as seed dispersers is well known, they may also drive large-scale processes that determine forest structure through the creation of elephant trails and browsing the understory, allowing larger, carbon-dense trees to succeed. Multiple scales of lidar were collected by NASA in LopĂ© National Park, Gabon from 2015 to 2022. Utilizing two airborne lidar datasets in an African forest elephant stronghold, detailed canopy structural information was used in conjunction with elephant trail data to determine how forest structure varies on and off trails. Forest along elephant trails displayed different structural characteristics than forested areas off trails, with lower canopy height, canopy cover, and different vertical distribution of plant density. Less plant area density was found on trails at 1âm in height, while more vegetation was found at 12âm, compared to off trail locations. Trails in forest areas with previous logging history had lower plant area in the top of the canopy. Forest elephants can be considered as âlogging lightâ ecosystem engineers, affecting canopy structure through browsing and movement. Both airborne lidar scales were able to capture elephant impact along trails, with the high-resolution discrete return lidar performing higher than waveform lidar
Using multiscale lidar to determine variation in canopy structure from African forest elephant trails
Recently classified as a unique species by the IUCN, African forest elephants (Loxodonta cyclotis) are critically endangered due to severe poaching. With limited knowledge about their ecological role due to the dense tropical forests they inhabit in central Africa, it is unclear how the Afrotropics are influenced by elephants. Although their role as seed dispersers is well known, they may also drive large-scale processes that determine forest structure through the creation of elephant trails and browsing the understory, allowing larger, carbon-dense trees to succeed. Multiple scales of lidar were collected by NASA in LopĂ© National Park, Gabon from 2015 to 2022. Utilizing two airborne lidar datasets in an African forest elephant stronghold, detailed canopy structural information was used in conjunction with elephant trail data to determine how forest structure varies on and off trails. Forest along elephant trails displayed different structural characteristics than forested areas off trails, with lower canopy height, canopy cover, and different vertical distribution of plant density. Less plant area density was found on trails at 1âm in height, while more vegetation was found at 12âm, compared to off trail locations. Trails in forest areas with previous logging history had lower plant area in the top of the canopy. Forest elephants can be considered as âlogging lightâ ecosystem engineers, affecting canopy structure through browsing and movement. Both airborne lidar scales were able to capture elephant impact along trails, with the high-resolution discrete return lidar performing higher than waveform lidar
Landscape-scale benefits of protected areas for tropical biodiversity
We are indebted to numerous local communities, PA and government agency staff, research assistants, and other partners for supporting the field data collection. Research permissions were granted by appropriate forestry and conservation government departments in each country. Special thanks is given to the Sarawak State Government, Sarawak Forestry Corporation, Forest Department Sarawak, Sabah Biodiversity Centre, the Danum Valley Management Committee, the Forest Research Institute Malaysia (FRIM), the Smithsonian Institute and the Tropical Ecology Assessment and Monitoring (TEAM) network, Sarayudh Bunyavejchewin, and Ronglarp Sukmasuang. Support was provided by the United Nations Development Programme, NASA grants NNL15AA03C and 80NSSC21K0189, National Geographic Societyâs Committee for the Research and Exploration award #9384â13, the Australian Research Council Discovery Early Career Researcher Award DECRA #DE210101440, the Universiti Malaysia Sarawak, the Ministry of Higher Education Malaysia, Nanyang Technological University Singapore, the Darwin Initiative, Liebniz-IZW, and the Universities of Aberdeen, British Columbia, Montana, and Queensland.Peer reviewedPostprin
Perceptions of older people among Chinese adolescents: conceptual and methodological issues
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